An ultra high performance liquid chromatography-tandem mass spectrometry method for the quantification of linagliptin in human plasma

A simple, rapid, sensitive, reliable and selective ultra high performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) method was developed for the quantification of linagliptin (LGN) in human plasma. LGN and its deuterated internal standard (IS) LGN-d4 were extracted from a low-plasma sample (volume: 300 mu L) by a simple liquid-liquid extraction protocol. Efficient estimation of the analyte and IS at a mean retention time (RT) of 1.75 and 1.74 min respectively, with a rapid 3.5 min run time per sample was chromatographically established on a Gemini C18 (100 mm x 4.6 mm, 3 mu) column under simple isocratic elution conditions, using a mixture of 10 mM ammonium formate : methanol [20 : 80 (v/v)] delivered at a flow rate of 0.5 mL min(-1). Following the separation of the compounds, protonated precursor -> product ion transitions were monitored for LGN (m/z: 473.3 -> 420.1) and IS (m/z: 477.5 -> 424.3) on a triple quadrupole mass spectrometer, operating in a multiple reaction monitoring (MRM) mode. The most recent regulatory guidelines were adopted during the method validation. The method demonstrated very good analyte and IS recovery (not less than 71.0%), precision (<= 8.6% CV), accuracy (range: 86.7% to 95.6%) and linearity (r > 0.99) across a clinically relevant LGN plasma concentration range: 50.3 to 12 115.5 pg mL(-1). The validated method was successfully applied to pharmacokinetic study samples for measuring linagliptin plasma levels.